A UserStyle is at the same semantic level as a NamedStyle used in the context of a
WMS. In a sense, a named style can be thought of as a reference to a hidden UserStyle
that is stored inside of a map server.

A portrayal catalog consits of a set of feature portrayal objects. Many may
exist for each feature type that may occur in the dataset. each feature object
has assigned a set of portrayal rules.

isDefault

The IsDefault element identifies whether a style is the default style of a layer, for use in
SLD ‘library mode’ when rendering or for storing inside of a map server. IsDefault uses
“1” or “true” for true and “0” or “false” for false. The default value is “0”.